Explanation for Rusting of Iron Nail Project!

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KarMark12
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Joined: Thu Jun 03, 2021 3:50 am
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Explanation for Rusting of Iron Nail Project!

Post by KarMark12 »

Hello! I am currently working on a project about rusting of iron nails and how the corrosion changes depending on the metal used to 'protect' (wrap) the iron nails with. The reactions in this experiment rely on normal iron being Iron(III) and rusted iron leeching a form of Iron(II).

The experiment is fairly qualitative, and involves use of the reaction between potassium ferricyanide and Iron(II) which creates a pigment known as Prussian Blue, Turnbull Blue or in German 'Berliner Blau'.

For more information on this reaction see this link:
https://chem.libretexts.org/Bookshelves ... on__(Fe³⁺)

The idea is to use several metals (I used copper, aluminium and magnesium) to wrap a thin layer around the nail which 'protects it' from being corroded.

The experiment was set up by creating agar plates with 0.1Molar of HCL (in order to catalyse the corrosion process and draw out the Iron) along with a small amount of Potassium ferricyanide (IMPORTANT: not ferrocyanide). The potassium ferricyanide is supposed to make the rust visible by turning it a dark blue colour (Prussian blue).

Setup:
1x control plate with just one unprotected iron nail
1x plate with iron nail wrapped with aluminium wire
1x plate with iron nail wrapped with copper wire
1x plate with iron nail wrapped with flexible magnesium ribbon

What should happen is that over the course of 24 or so hours, the control should cause the plate to turn a vivid blue colour and all the nails with different metals should change the amount of blue that infiltrates the agar. When I conducted this experiment it worked really well and the blue was visible on all of the plates except for the Magnesium one because as per my teachers instructions, this should have been the most protected one (i.e. the one that rusted the least). Everything went fine, except for the plate with a copper bound nail, which demonstrated even more corrosion than the control. Thinking this was an error, I went to my teacher to ask if I should redo that trial, to which they stated that this was an excellent result and that it was supposed to be this way. I'm afraid I don't understand why this is the case. Any explanation would be much appreciated.

P.S.
I do not have a very high level of chemistry, I understand Ionic bonding, dissociation, and a little bit about redox reactions.
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